Abstract: In order to enhance the flocculation performance of polyacrylamide （PAM）， the inorganic cationic colloid groups were grafted onto the PAM molecular chain for organic-inorganic hybrid modification. Hybrid modified aluminum hydroxide polyacrylamide （Al（OH）3-PAM） and magnesium hydroxide polyacrylamide （Mg（OH）2-PAM） were synthesized using in-situ polymerization of aqueous solution. The structure of hybrid modified PAM was analyzed and characterized by infrared spectroscopy. The viscosity average molecular weights of Al（OH）3-PAM and Mg（OH）2-PAM were determined to be 2.7 million and 3.2 million using the ubbelohde viscometer. The flocculation and sedimentation performance of the synthesized flocculant was studied by sedimentation test with the kaolin pure mineral of -0.038 μm. When the flocculant dosage is 70 g/t， the initial settling velocity in the first ten seconds of Al（OH）3-PAM and Mg（OH）2-PAM are 7.713 mm/s and 11.181 mm/s， respectively， while that of 8 million cationic polyacrylamide （CPAM） is only 3.923 mm/s. The flocs after the action of Al（OH）3-PAM and Mg（OH）2-PAM is smaller and denser than that produced by CPAM. The performance of hybrid modified polyacrylamide is significantly better than that of CPAM and aluminum salt-PAM as well as magnesium salt-PAM composite flocculant， and the hybrid modified polyacrylamide Mg（OH）2-PAM with higher molecular weight has better flocculation and sedimentation performance.

Key words: Polyacrylamide, Hybrid modification, Flocculation sedimentation test, Cationic colloid groups